N-phosphonomethylglycine, otherwise known as glyphosate, is well known in the art as an effective post-emergent foliar applied herbicide. Glyphosate is an organic compound with three acidic groups and in its acid form is relatively insoluble in water. Glyphosate is, therefore, normally formulated and applied as a water-soluble salt. Although monobasic, dibasic and tribasic salts of glyphosate can be made, it has generally been preferred to formulate and apply glyphosate, in the form of a monobasic salt, for example as a mono-(organic ammonium) salt such as the mono (isopropylamine), often abbreviated to IPA salt.
The present application refers to and is applicable to all glyphosate salts including, but not limited to, “ammonium”, “monoammonium” and “diammonium” salts of glyphosate. For example, the glyphosate salts useful in the present context include, but are not limited to salts of isopropylamine, monoethanolamine, diethanolamine, potassium, ammonium, trimesium, or mixtures thereof. Glyphosate rates and concentrations given herein, even where the glyphosate is present as a salt or salts, are expressed as acid equivalent (a.e.) unless the context demands otherwise.
Glyphosate salts generally require the presence of a suitable surfactant to improve bioefficacy and enhance overall herbicidal performance. The surfactant may be provided in the concentrate formulation, or it may be added by the end user to the diluted spray solution. The choice of surfactant is very important since there are wide variations among surfactants in their ability to enhance the herbicidal efficacy of glyphosate.
The herbicidal efficacy of glyphosate salt solutions is highly dependent upon two factors: selecting a suitable surfactant and providing an effective (as high a concentration as possible) amount of that surfactant in the concentrate formulation. Glyphosate itself is mild to the eyes, has low aquatic toxicity and is readily biodegradable. Alkylamine based surfactants have been used and have provided excellent bioefficacy enhancing ability to glyphosate. These surfactants may under certain conditions exhibit higher eye irritation potential than various other surfactants, but are nonetheless suitable and safe for use. However, alternatives to alkylamine based surfactants having lower eye irritation properties and lower toxicity to aquatic life would be advantageous in certain circumstances.
It is known to those skilled in the art that finding a suitable surfactant with good efficacy enhancing property for glyphosate is difficult. However, finding a suitable surfactant with low eye irritation and aquatic toxicity properties in addition to good efficacy enhancing property is more difficult. Very few known surfactants (e.g., alkyl polyglycoside, short chain phosphate ester, alkylamine oxide and alkyl betaine) with good eye irritation and aquatic toxicity properties have been used in glyphosate formulations. However, these surfactants are not very efficacious for glyphosate.
Accordingly, it is desirable to develop a suitable surfactant with low eye irritation and aquatic toxicity properties in addition to good efficacy enhancing property for glyphosate. These and other objectives are met by the surfactants and herbicidal formulations of the present invention.